Tiny new feature: Checkboxes in a message.
No, I'm not gonna make it a full blown task list app 
but it happens quite often, that my wife sends me a list of groceries when I'm walking to the supermarket. This way I'm now able to check, what I have already in my cart so I don't forget anything.
It works by sending special reactions under the hood. So anyone with reaction sending permissions in a room can check any box from any sender.
What do you think?